<!DOCTYPE html>
<html>
<head>
    <title>Simple Website</title>
</head>
<body>
    <input type="checkbox" name="checkbox" id="checkbox">
    <label for="checkbox">Check me</label>
    <input type="text" name="textfield" placeholder="Enter text here">
    <iframe src="outer-iframe.html"></iframe>
</body>
</html>
